A015877 Numbers k such that sigma(k) = sigma(k+9).

14, 16, 46, 446, 1146, 26766, 35805, 143605, 179086, 185946, 437745, 1187725, 1194646, 1327086, 1746946, 2201806, 2893605, 3003385, 3574725, 3730125, 4053586, 4928385, 5715325, 6220305, 7507946, 9423645, 9897186

Offset: 1

Author

Robert G. Wilson v

Keywords

• nonn

Links

• Donovan Johnson, Table of n, a(n) for n = 1..200

Crossrefs

Cf. A002961, A007373, A015861, A015863, A015865, A015866, A015867, A015876, A015880, A015881, A015882, A015883, A181647.

Programs

Mathematica

Select[Range[10000000], DivisorSigma[1, #]==DivisorSigma[1, # + 9] &] (* Vincenzo Librandi, Mar 10 2014 *)
Position[Partition[DivisorSigma[1,Range[10^7]],10,1],?(#[[1]] == #[[10]]&),{1},Heads->False]//Flatten (* _Harvey P. Dale, Aug 25 2016 *)

PARI

is(n)=sigma(n)==sigma(n+9) \\ Charles R Greathouse IV, Mar 09 2014